Steam-powered injectors are generally known and used for pumping condensate or other liquids into a boiler for a steam engine or steam cycle system, but the transducer in such systems is powered by steam, and the injector is merely a convenient pump for delivering liquid to the boiler. The invention involves recognition of a way that the pumping power of an injector can be used to pump liquid around a path leading through a rotatably driven transducer to extract energy from the moving liquid while using the steam merely to power the injector. This eliminates the need for a condenser and allows the entire system to be insulated and made more efficient than conventional steam cycle systems. The invention thus aims at improvements in simplicity, economy, and efficiency in a thermodynamic system.